Use lock-free lazy initialization for static histogram references

net/base/cookie_monster.h

Index: net/base/cookie_monster.h
===================================================================
--- net/base/cookie_monster.h	(revision 80382)
+++ net/base/cookie_monster.h	(working copy)
@@ -469,17 +469,17 @@
 
   // Histogram variables; see CookieMonster::InitializeHistograms() in
   // cookie_monster.cc for details.
-  scoped_refptr<base::Histogram> histogram_expiration_duration_minutes_;
-  scoped_refptr<base::Histogram> histogram_between_access_interval_minutes_;
-  scoped_refptr<base::Histogram> histogram_evicted_last_access_minutes_;
-  scoped_refptr<base::Histogram> histogram_count_;
-  scoped_refptr<base::Histogram> histogram_domain_count_;
-  scoped_refptr<base::Histogram> histogram_etldp1_count_;
-  scoped_refptr<base::Histogram> histogram_domain_per_etldp1_count_;
-  scoped_refptr<base::Histogram> histogram_number_duplicate_db_cookies_;
-  scoped_refptr<base::Histogram> histogram_cookie_deletion_cause_;
-  scoped_refptr<base::Histogram> histogram_time_get_;
-  scoped_refptr<base::Histogram> histogram_time_load_;
+  base::Histogram* histogram_expiration_duration_minutes_;
+  base::Histogram* histogram_between_access_interval_minutes_;
+  base::Histogram* histogram_evicted_last_access_minutes_;
+  base::Histogram* histogram_count_;
+  base::Histogram* histogram_domain_count_;
+  base::Histogram* histogram_etldp1_count_;
+  base::Histogram* histogram_domain_per_etldp1_count_;
+  base::Histogram* histogram_number_duplicate_db_cookies_;
+  base::Histogram* histogram_cookie_deletion_cause_;
+  base::Histogram* histogram_time_get_;
+  base::Histogram* histogram_time_load_;
 
   CookieMap cookies_;